1. Field of the Invention
The present invention relates to a nonaqueous electrolyte battery.
2. Description of the Related Art
Nonaqueous electrolyte batteries using a lithium metal, lithium alloy, lithium compound or carbonaceous materials as the negative electrode active material are expected as high energy density batteries and earnest studies are being made as to these nonaqueous electrolyte batteries. Lithium ion batteries comprising a positive electrode containing LiCoO2 or LiMn2O4 as an active material and a negative electrode containing a carbonaceous material that absorbs and release lithium ions have been widely put to practical use in portable telephones so far.
In the case of mounting a battery in vehicles or electric trains, on the other hand, materials superior in chemical or electrochemical stability, strength and corrosion resistance are desired as the materials of the positive electrode or negative electrode from the viewpoint of storage performance at a high temperature (60° C. or more), cycle performance and long term reliability of high output.
Therefore, it is found from the above descriptions that lithium ion batteries pose a large problem concerning high-temperature durability necessary to mount them on a car and the like. Particularly, it is difficult to use these lithium ion batteries by mounting them on the engine room of vehicles in place of lead batteries.
Various attempts have been made to improve negative electrode characteristics. JP-A 2002-42889 (KOKAI) discloses that a negative electrode having a structure in which a current collector made from aluminum or an aluminum alloy is made to carry a specified metal, alloy or compound is used in a nonaqueous electrolyte secondary battery.
On the other hand, JP-A 2001-143702 (KOKAI) discloses that primary particles of lithium titanate compound represented by the formula LiaTi3−aO4 (0<a<3) and having an average particle diameter less than 1 μm are coagulated into granules having an average particle diameter of 5 to 100 μm to form secondary particles, which are used as a negative electrode active material. Also, in JP-A 2001-143702 (KOKAI), there is the description that the coagulation of secondary particles is suppressed by the use of this negative electrode active material, which increases the production yield of a negative electrode having a large area for a large scale battery.
Also, studies are being made as to the development of a higher capacity positive electrode material to develop a battery having a high energy density. As the positive electrode materials substituted for lithium cobalt oxides such as LiCoO2, for example, lithium/nickel/cobalt oxides such as LiNixCo1−xO2 and lithium/manganese oxides such as LiMnO2 are being developed for practical use. However, these materials have problems concerning cycle life performance and thermal stability under high temperatures.